1. Field of the Invention:
The present invention relates to a welding transformer and a method of manufacturing such a welding transformer, and more particularly to a high-frequency welding transformer, which is small in size and light in weight, for use in an inverter-type resistance welding machine, and a method of manufacturing such a high-frequency welding transformer.
2. Description of Background Art:
Heretofore, resistance welding robots are widely used on automobile production lines, for example, in order to supply large electric currents to workpieces which are to be welded.
An inverter-type DC resistance welding machine has been employed for such a welding robot. In the inverter-type DC resistance welding machine, a direct current is converted into a high frequency alternating current which is then supplied to a welding transformer to lower its voltage. Then, the alternating current is rectified by a rectifying circuit into a direct current which is supplied to a welding gun arm. The direct current is first converted into the high-frequency alternating current because the welding transformer may be relatively small in size and light in weight since the cross-sectional area of the core of the welding transformer is inversely proportional to the frequency of the high-frequency alternating current.
One welding transformer of the above kind is disclosed in Japanese Utility Model Publication No. 61(1986)-33620, for example. The disclosed welding transformer comprises a primary coil composed of a number of turns, a transformer core, and a secondary coil composed of one turn and having a center tap. The welding transformer is in actual use in a frequency range from several hundred Hz to 1 KHz.